This invention relates to Smart Power MOSgated devices, and more particularly relates to a Smart Power circuit in which a unique reset signal for resetting the fault latch circuit after a fault is applied to the circuit input pin and in which the device off-signal input level cannot reset the fault latch of the circuit.
Smart Power devices are well known power switching devices in which a MOSgated device, typically a power MOSFET, is provided with "intelligence" such as circuits which monitor the device temperature, current and voltage conditions and turn the device off when fault conditions are measured or expected. One well known device of this type is the fully protected DMOS Power Switch manufactured by the International Rectifier Corporation, Type No. IRSF 3010, termed a SMARTFET Transistor. SMARTFET is a trademark of the International Rectifier Corporation, the assignee of this invention.
The device is formed monolithically in a three-pin TO 220 package. Other package styles can be used. The package has an input pin, a drain pin and a source pin. The operating power for the control circuits is provided from the input control signals at the input pin. The device is a fully protected monolithic N-channel, logic level power MOSFET with 80 ohms on-resistance and with built-in circuit protection against overcurrent, over-temperature, ESD and with active over-voltage protection.
The device employs a latching circuit which is integrated into the power FET chip, and which recognizes and memorizes the occurrence of an error and then removes the turn-on signal from the power MOSFET gate. The latch circuit is cleared and reset by holding the input low for a specified minimum duration. Therefore, if a fault condition persists, and the latch circuit is reset in the next cycle of operation, the device turns on into the fault condition and is tripped again, this condition lasting until the circuit is otherwise cleared.
This condition can be avoided by providing a separate reset pin for the package which receives a separate reset input signal. However, this would require a five-pin package and, further, would prevent the use of an SOT223 type package. It is very desirable, however, to make this device as a three-pin package which can be a drop-in replacement for other three-pin packages which are with or without intelligence circuits.